The invention relates to marine propulsion combination with improved cooling, to prevent over-heating.
Engine overheating in twin drive marine propulsion units is a long standing problem, particularly in,turns. Various prior attempts in solving the problem have centered around redesigns of the water inlet configuration structure. It has been found that this does not address the source of the problem. Furthermore, such redesigns of the water inlet configuration structure may be undesirable because of the tooling modifications required thereby, and because of increased drag in some designs.
In the present invention, it has been found that the source of the overheating problem is aerated water entering the water inlet, which in turn is due to the lifting strakes along the boat hull. The twin propulsion units are generally longitudinally aligned with respective strakes. It has been found that the configuration of the strakes creates a low pressure channel along the side of the strake. Air can enter at the water line and run along such low pressure path back to the end of the strake, where the air will spread in depth and width and provide a plume of aerated water. Since the propulsion units are in line with such strakes and plumes, the water inlets for the cooling system of the engine receive aerated water, reducing the volume of water entering the cooling system, thus resulting in engine overheating.
Improved cooling is provided by substantially diminishing the amount of aerated water supplied to the water inlets of the propulsion units.
In the present invention, the strake configuration is modified to eliminate the low pressure channel, to in turn eliminate the noted aerated water flow to the water inlets of the propulsion units. This in turn reduces the amount of air and increases the amount of water flowing into such inlets, to provide improved cooling.